But what about cloning? If someone were to use my DNA to make a clone, would that person be identical to me? This brings in the term, epigenetics, the fact that genes interact with their environments and produce different results, based on the variations in those encounters. Unless a clone can be raised in exactly the same conditions that I experienced, said creature would be distinct from me. There’s another factor that will have to be taken into account, but I’ll say more about that in a moment.

Of course, a person on life support is dependent on machinery for life, but such a person is not connected to another organism in the manner of a parasite. This category is complicated in that patients in a vegetative state are unlikely to recover and thereby are not able to live without being sustained continually and may be considered to fail in this category.

3. Life experience

Memory is a fundamental element of human existence. Speaking more broadly, who we are is, in part, what we have done. This is another way that twins or clones are different. Unless they do exactly the same actions throughout their lives, they will be distinct individuals. I’m not limiting this category to any particular length of time. The first action or memory is enough to qualify.

What of people who suffer from Alzheimer’s disease or similar forms of dementia? The disaster of those conditions is that over time they rob a person of the quality that makes us consciously distinct.

I propose the following:

A unique human being has at least two of those three elements.

Does an embryo or fetus during the first two trimesters qualify? No. It fails items two and three. How about a comatose patient? Yes. The person possesses the first two, regardless of whether the third remains extant. And a clone that is allowed to come to term and grow into adulthood? Yes. That person will certainly have the latter two characteristics and given enough time will also acquire the first, as described above.

While it is best to respect organisms who possess any of these three characteristics, human life requires at least two to qualify for full rights.